How do I create a wood texture?
As LukeD mentioned, you could make your way with what he pointed out. Depending on your skill level, you may succeed or be completely discouraged.

There's a full tutorial from Andrew Price (blender guru) teaching the whole work flow of the steps mentioned in the later comment.
https://www.blenderguru.com/tutorials/how-to-create-realistic-bread

Yep, it's not for a rough bark but the work flow should help you taking care of some details and difficulties you may encounter during the process.
Replace all the words "Bread" with "Wood" and you'll be good to go!
I guess I saw some wood textures that may help you out on textures.com, it's free for low res.

Good luck!